Document artificial-block.rs

Author: jieyouxu

tests/ui/artificial-block.rs

@@ -1,5 +1,30 @@
+//! Check that we don't get compile errors on unreachable code after the `{ ret 3; }` artificial
+//! block below. This test is run-pass to also exercise the codegen, but it might be possible to
+//! reduce to build-pass or even check-pass.
+//!
+//! This test was introduced as part of commit `a833f152baa17460e8414355e832d30d5161f8e8` which
+//! removes an "artificial block". See also commit `8d381823e2aa1524eabeb3219d7dc1d5007e6096` for
+//! more elaboration, produced below (this is outdated for *today*'s rustc as of Dec 05, 2024, but
+//! is helpful to understand the original intention):
+//!
+//! > Return a fresh, unreachable context after ret, break, and cont
+//! >
+//! > This ensures we don't get compile errors on unreachable code (see
+//! > test/run-pass/artificial-block.rs for an example of sane code that wasn't compiling). In the
+//! > future, we might want to warn about non-trivial code appearing in an unreachable context,
+//! > and/or avoid generating unreachable code altogether (though I'm sure LLVM will weed it out as
+//! > well).
+//!
+//! Since then, `ret` -> `return`, `int` -> `isize`, `assert` became a macro.
+
 //@ run-pass
 
-fn f() -> isize { { return 3; } }
+fn f() -> isize {
+    {
+        return 3;
+    }
+}
 
-pub fn main() { assert_eq!(f(), 3); }
+fn main() {
+    assert_eq!(f(), 3);
+}